The present invention generally pertains to shaped-charge devices and is particularly directed to improving the accuracy of the trajectory of the jet of liner material expelled therefrom upon detonation of the charge of explosive material contained thereto.
Shaped-charge devices are described in U.S. Pat. Nos. 4,724,767 to Aseltine, 4,436,033 to Precoul and 4,498,367 to Skolnick et al. and by Aseltine "Design of a Charge with a Double, Inverse Velocity Gradient", 13th International Symposium on Ballistics, Stokholm, 1-3 Jun. 1992, pp. 505-512 (WM-25/1-25/8).
A typical shaped-charge device includes a case defining an axisymmetrical forwardly-opening cavity uniformly disposed about a central axis; an axisymmetrical, homogeneous-material, liner of variable thickness defining a forwardly-opening cavity having a closed apex, with the cavity being uniformly disposed within the casing about the central axis; and explosive material symmetrically disposed between the casing and the liner; wherein the liner is so shaped that in response to the explosive material being detonated to thereby explode, the liner is progressively collapsed inward by the exploding material to be formed into a fluid jet of the homogeneous liner material that is forwardly expelled at a varying velocity from the casing along the central axis, with the forward portion of the jet being squeezed from the apex of the collapsing liner.
One use of a shaped-charge device is to provide a high velocity jet for penetrating a metal casing, such as a well casing. Aseltine has described the formation of the jet in such a manner that the jet includes at least one bulge at an intermediate position within the jet so as to provide enough concentrated mass at such intermediate position as to be able to penetrate the casing. The bulge applies the amount of pressure against the casing that would be applied if the explosive charge were larger and the jet did not include a bulge and thereby enables use of a smaller charge to achieve penetration.
Another use of a shaped-charge devices is to detonate buried munitions, such as land mines, by penetrating the casing of the munition with a high velocity jet expelled from a shaped-charge device. Because the shaped-charge device is disposed on the ground surface whereby the jet has to travel through a depth of soil before contacting the buried munition, the jet must be expelled at a high velocity and include at least one bulge for penetrating and detonating the buried munition; and it is desired that the trajectory of the jet not significantly deviate from the central axis of the shaped-charge device so that fewer shaped-charge devices are required for detonating all of the munitions buried within a given area. It has been ascertained that the trajectory of the jet expelled from the shaped-charge device described by Aseltine frequently deviates from the central axis of the shaped-charge device because as the bulge is being formed within the jet, the homogeneous material with which the jet is being formed frequently bunches up in such a manner as to cause the jet to deviate from the central axis.